WASHINGTON -- Police and prison guard brutality and excessive force cases in the United States increased 25 percent since 2001, U.S. Justice Department statistics showed.

But it's unclear whether the rise is due to increased misbehavior by law enforcement or more aggressive prosecution, University of Toledo law professor and police-conduct analyst David Harris told USA Today.

National Fraternal Order of Police Executive Director James Pasco said there's worry about reduced standards and promotions of inexperienced officers, USA Today said. Police nationwide have reported trouble filling vacancies particularly as police recruits have opted for military service.